Today, many new settlers, equipping the apartment, are forced to carry out additional work, including the soundproofing of their homes, because the standard materials used make it possible only to partially hide what is happening in your own house, and not be interested against the communication of neighbors.
The
speed of sound in solids is affected at least by the density and elasticity of the substance opposing the wave. Therefore, when equipping the premises, the layer adjacent to the load-bearing wall is made soundproof with “puffs” from above and below. It allows you to reduce
the noise level in decibels, sometimes more than 10 times. Then, basalt mats are laid, and on top are drywall sheets that reflect the sound outside the apartment. When a sound wave "flies" to such a structure, it damps in the insulator layers, which are porous and soft. If the sound has great power, then the materials absorbing it can even heat up.
Elastic substances, such as water, wood, metals, transmit sound vibrations well, so we hear beautiful “singing” of musical instruments. And some nationalities in the past determined the approach, for example, of horsemen, putting their ears to the ground, which is also quite elastic.
The speed of sound in km depends on the characteristics of the medium in which it propagates. In particular, the process may be affected by its pressure, chemical composition, temperature, elasticity, density and other parameters. For example, in a steel sheet, a sound wave travels at a speed of 5100 meters per second, in a glass - about 5000 m / s, in a tree and granite - about 4000 m / s. To convert speed to kilometers per hour, you need to multiply the figures by 3600 (seconds per hour) and divide by 1000 (meters per kilometer).
The speed of sound in km in an aqueous medium is different for substances with different salinity. For fresh water at a temperature of 10 degrees Celsius it is about 1450 m / s, and at a temperature of 20 degrees Celsius and the same pressure it is already about 1490 m / s.
The salty medium differs by a known higher speed of sound vibrations.
Sound propagation in air also depends on temperature. With a value of this parameter equal to 20 degrees Celsius, sound waves travel at a speed of about 340 m / s, which is about 1200 km / h. And at zero degrees, the speed slows down to 332 m / s. Returning to our insulators for an apartment, we can find out that in a material such as cork, which is often used to reduce external noise, the speed of sound in km is only 1800 km / h (500 meters per second). It is ten times lower than this characteristic in steel parts.
A sound wave is a longitudinal vibration of the medium in which it propagates. When, for example, a melody of a piece of music passes through an obstacle, its volume level decreases, because the
amplitude of the oscillations changes
. At the same time, the frequency remains the same, so we hear the female voice as female, and the male voice as male. The most interesting is the place where the speed of sound in km is close to zero. This is a vacuum in which waves of this type hardly propagate. To demonstrate how this works, physicists put a ringing alarm clock under a cap from which air is pumped out. The greater the thinness of the air, the quieter the ringer is heard.